Polymer compositions having pesticidal properties are useful for making pesticide-treated articles such as insecticide-treated nets which repel, disable, and/or kill disease-spreading insects coming into contact with these types of netting.
A conventionally treated insecticidal net is typically made by dipping the net in an insecticide. However, these nets tend to lose their insecticidal effect over time and usually require re-treating with an insecticide at least once a year or after about three washes. The World Health Organization (WHO) has issued a global guidance for the use of insecticide-treated mosquito nets to protect against malaria, and recommended that such insecticidal nets be long-lasting, i.e., retain its biological activity without re-treatment for at least 20 WHO-standard washes under laboratory conditions and 3 years of recommended use under field conditions.
A long-lasting insecticide-incorporated net, unlike conventionally treated nets, is made with a netting material having insecticide incorporated within or bound around its fibers. This can be accomplished by combining the active insecticidal ingredient with a polymer via a masterbatch to be added to a polymer base, which then can be formulated into an insecticide-incorporated fiber and subsequent product. Insecticide-incorporated nets have several advantages over conventionally treated nets. For one, having insecticide incorporated into the netting material substantially reduces the frequency of re-treatment needed. Reducing the number of re-treatments lowers costs, reduces health and safety risks associated with exposure to insecticide during re-treatment, and lessens the environmental impact. In addition, because the active insecticidal ingredient gradually and constantly migrates within the netting material to the yarn surface, insecticide-incorporated nets are expected to be effective for the entire lifetime of the net (at least three years).
Long-lasting insecticide-incorporated nets can be made starting with a masterbatch containing a pyrethroid and a polymer. WO2004/089086 relates to a composition having at least one pyrethroid and an ethylenically-unsaturated substance. The composition is said to be useful for the preparation of a premix and an insecticidal and acaricidal article of fibrous or sheet-like form with a polymeric material. The reference also describes a method for preparing the composition, premix, and the article. The composition described therein can be used as an additive for a polymeric composition in order to obtain a final material able to release an insecticidal flux. The composition is useful for the production of various articles such as fibers, mosquito nets, and other extruded items such as to films, thermo-formed or injection-molded articles.
WO2008/141928 relates to a material having insecticidal and acaricidal properties containing from 99.95% by weight to 70.0% by weight of a propylene-based polymer having a Melt Flow Rate (MFR) between 11 and 40 (ISO 1133); isotactic pentads (mmmm) higher than 90%; from 0.05% to 30% by weight of an adduct of formula T1-T2 resulting from the condensation of T1 and T2, wherein T1 comprises at least one pyrethroid substantially stable up to a temperature of at least 150° C.; T2 is an ethylenically unsaturated substance that is a surfactant, vinyl phosphate, or both. This reference states that the polypropylene-based polymer can be obtained by using a titanium and magnesium-based catalyst system or by a metallocene-based catalyst system.
There is a need for compositions containing a pesticide, e.g., a pyrethroid, and propylene-based polymer having improved processability. Propylene-alpha-olefin copolymers are a versatile thermoplastic material that can accept high filler levels and is compatible with many processing techniques. Applicant has found that when propylene-alpha-olefin copolymers are used as a carrier in a pesticidal composition, the masterbatch loading can be higher compared to when standard isotactic polypropylene is used and, furthermore, the masterbatch distribution into polypropylene matrix can be enhanced when processed under normal mixing conditions.